The present application relates to a data communications system and a data communications method that are suitably applicable to the data communication to be executed between client and server in an on-demand manner.
For example, online transactions based on networks, such as the sale of products over the Internet has been gaining popularity. So-called online trading is one of these online transactions. In transactions based on data that change from time to time, such as transactions concerning shares, the information when and who has executed particular transactions becomes very important.
These days, methods are used in which the past transactional information is managed by servers and transactional records are reported to users via electronic mail, for example. Searching the past transactional information for transaction times and traders provides the information about the timing and time zone in which transactions can be executed.
Also, a time stamp system is disclosed in which setting information, such as database connection information and external clock source connection information, is stored in a setting information file after encrypting the setting information with an encryption key and password, the encrypted setting information is read from the setting information file and decrypted to execute database connection processing or external time source connection processing for example, thereby preventing the setting information from manipulation attack (refer to Japanese Patent Laid-open No. 2004-266537).
However, with the above-mentioned method in which past transactional information is managed by a server, there remains a possibility of manipulation attack against the past transactional information stored in the server. Therefore, this method involves a problem that, with services of limited tradable times and time zones, it is difficult to determine whether or not trading was executed in a particular time and a particular time zone.
The technique disclosed in patent document 1 just discloses a time stamp service based on a public key encryption technique. Therefore, the disclosed technique involves problems that an embodied system may be made large scale and this system indicates just that particular data existed at a particular point of time, not that communication was executed at the particular point of time, thereby making it difficult to find particular trade timings and traders if this data is referenced.